In the specific technical field, there are well-known frames for spectacles in which the articulation of the arms to the front mount is carried out by means of hinge devices having respective pins and eye-like seats which are associated with each other in a rotatable manner, the hinge elements of those devices being fixedly joined suitably to the arm and the lug of the frame.
That type of solution, in the multiple versions thereof available in the prior art, conventionally involves some limitations, including the possible undesirable loosening of the screw or the hinge pin, the need to produce a plurality of components which are required for the hinge articulation, the spatial requirement dictated by the necessary components, and the weight itself of the hinge device which is not very suitable for use in frames of the lightweight type.
There are further known solutions for the articulation of the arm to the front lug of the frame which do not provide for any conventional hinge structure of the above-mentioned type. An example is known from FR 1009345, in which there is described a system for the articulation with resilient locking of the arm to the lug. It provides for the arm end directed towards the front lug to be divided into three separate portions over a sufficient length to provide them with a mutual resilient behaviour. The folded end of the central portion together with the lateral portions retain the arm in an articulated manner about a pin-like formation which is provided on the frame.
Another type of solution is set out in JP 2011/095691, in which one or more elongate elements produced from a resilient sheet are formed, by cutting, at the end of the arm directed towards the lug and are provided to engage with the folded ends thereof with corresponding through-openings formed through the lug portion, thereby producing the retention in an articulated manner of the arm with respect to the lug of the frame.
However, both those last solutions involving articulation of the arm have some limitations. In the first place, the connection of the arm to the lug is not particularly stable, in all the positions of the arm between the extreme opening and closure conditions on the frame, in particular the arm tends to have a relative movement with respect to the lug (transversely to the front plane of the frame when the arm is open), bringing about a type of relative oscillation between the arm and the lug, which may, in addition to not being technically acceptable as a result of the poor stability of the connection and the excessive play of the connection which it involves, also compromise the wearing comfort of the frame.
Another limitation is linked with the fact that the arm can be exposed to accidental disconnection from the lug, mainly owing to the fact that the relative connection forces are generated exclusively by the resilient urging of the sheet-like element formed on the arm. A possible accidental impact or pulling action of such a magnitude as to overcome the resilient connection force may bring about the disarticulation of the arm from the lug with detachment thereof from the frame.